MOSCOW, Russia - On Thursday, U.S. said that its forces had targeted forces loyal to Syrian leader Assad with airstrikes in a bid to protect its forces in the war-torn country.

In what became the first such close confrontation between U.S. forces and fighters backing President Bashar Assad, U.S. officials stated that the country’s military launched airstrikes against pro-Syrian government forces in southern Syria.

This was also the second time that the U.S. military launched airstrikes against pro-Assad forces under the Trump administration.

Military officials said they targeted and destroyed vehicles that were advancing near an area of southern Syria where U.S. forces are currently deployed.

The strikes reportedly hit a regime-allied militia mixed with Syrian government forces outside a base called Tanf, near the Jordanian border where U.S. Special Forces have been deployed, along with a unit of Syrian rebels.

However, lashing out on Friday, Russia and Syria both condemned the attack, with Russian forces accusing that the U.S. airstrikes had killed civilians.

Making the comments on Syrian state TV, a Syrian military official said that the airstrike by the U.S.-led coalition on a government military position near the border with Jordan had killed several soldiers and caused material damage.

The official cited by Syrian state TV said that the Syrian army was fighting terrorism and no one else had the right to decide in which areas it can carry out operations.

Further, Russia also criticized the strike, with the country’s Deputy Foreign Minister Gennady Gatilov Gatilov accusing the U.S. of violating Syria’s sovereignty and alleging the airstrike hit civilians.

Later, Deputy Foreign Minister Gennady Gatilov said he was referring to a separate U.S.-led coalition strike on Wednesday that reportedly killed dozens of civilians.

The coalition meanwhile has denied the attack took place.

Speaking to reporters on Thursday, U.S. Defense Secretary Jim Mattis said the U.S. would defend its troops in case of "aggressive" steps against them.

Commenting on whether the airstrike represented an increase in the U.S. role in the Syrian war, Mattis said, "We are not increasing our role in the Syrian civil war, but we will defend our troops. And that is a coalition element made up of more than just U.S. troops, and so we will defend ourselves (if) people take aggressive steps against us."

In addition, Operation Inherent Resolve, the U.S.-led campaign against the Islamic State of Iraq and Syria (ISIS), said in a statement that "the coalition struck pro-regime forces that were advancing well inside an established de-confliction zone" and "posed a threat to U.S. and partner forces."

Reports noted that the 5th Special Forces Group, that have been training pro-Western rebel groups, consisting of ‘Vetted Syrian Opposition’ to fight ISIS for six months now, also accompany the rebels in combat missions against the militants.

Meanwhile, a rebel commander quoted in a BuzzFeed report said that the Syrian regime and its allies — including Iranian forces, Shiite militia, and Hezbollah — are also based about 40 miles outside Tanf.

This, he noted, allows them easy access to Tanf via a highway that cuts through the desert.

Meanwhile, the airstrikes were said to have targeted the Syrian regime forces after they breached a "de-confliction zone.”

The de-confliction zone around the base is the area that the coalition has communicated to the Russians to stay away from.

The report noted that the U.S.-led coalition commander, in a show of force, dispatched two U.S. aircrafts to warn off the pro-Assad forces out of the zone.

However, the airstrike was launched when the forces failed to respond.

Five of the 13 vehicles that breached the zone, came within 29 kilometers of the base at about midnight EST Thursday when the aircraft were dispatched.

In March, Trump ordered a U.S. strike of 57 Tomahawk missiles against President Assad held al-Shayrat air base in retaliation to a chemical weapons attack that was blamed on the country’s regime.

Reports noted that the U.S. strike marks a new approach in the complicated war zone.

This was the first strike by the coalition on pro-Assad forces in the battlefield.

The coalition had so far focussed its military operations on Islamic State militants and al-Qaida-linked groups.